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Earthworm Ecosystems: What do Earthworms Like to Eat?
Category:Biology in elementary schools What do Earthworms Like to Eat? Student worthiness Brand new and untested Category:Biology in elementary schools Primary biological content area covered Worms; behavior; ecosystems; hypothesis testing; running experiments; data collection and interpretation This experiment will introduce students to one form of ecosystem as well as demonstrate how earthworms and the foods they eat affect the environment in which they live. Materials Teacher Materials: Pre-Made Soda Bottle Ecosystem (Directions Below) *2 Liter Soda Bottle *Gravel *Sand (any type except Perlite) *Bedding Material *Dark Potting Soil *2 pie plates or any type of water-catching plate *2 pieces of tin foil *5-6 Dew Worms (Lumbricus terrestris) *Electric Drill (optional) *Utility Knife Student Materials: *2 large, clear, plastic drinking straws *1 large plastic tub (rinsed out margarine tub) *potting soil (from your ecosystem) *bedding material (same as from your ecosystem) *water (used to keep the dew worms moist) *lettuce *apples *bread *lime or lemon *ruler *duct tape *scissors Handouts # Take your plastic tub and poke four holes the size of drinking straws into the side of the tube with teacher supervision. (Refer to figure 1 or use the website below to print out multiple copies) #With the scissors, cut the two plastic straws in half #Use the duct tape to seal one end of the straw to form a feeding tub for the worms. #Take the four different types of food and prepare them so that they can fit into the straws. #Fill each of the four straws with food, one type of food for every straw. #Insert the straws through the holes in the plastic tub. #Secure the straws into the tub with duct tape.Be sure not to block the opening in the straw while securing them to the tub. #Fill the plastic tub with a generous amount of soil and bedding from your ecosystem. ** Make sure the soil completely covers the food tubes. #Place five or six worms into the plastic tub. # Moisten the soil # Observe the feeding tubes after about fifteen minutes and record your findings. # Once you have observed which foods the worms like and which ones they don't return the worms into their ecosystem. #Discuss your findings as a group. Student Handout: A helpful way to get the students involved and informed before the experiment is to give each group a handout like this (Handout 1), which gives them some background knowledge about ecosystems and earthworms. This activity also allows the students to use the knowledge that they are acquiring in their science class as relation to the experiment they will be conducting. Then, using the second worksheet (Handout 2) at the end of the experiment, students can use the knowledge they gained in the beginning and from the experiment and from previous knowledge to answer the questions on the sheet. By making simple worksheets like this, you will have a great addition to your project that helps bring out the content of the lesson and making it known to students. Description of activity During this activity teachers will prepare an ecosystem for dew worms prior to performing the experiment above.Once the ecosystems have been made and the dew worms have acclimated to their new homes the experiment can begin. Students will form a hypothesis as to which foods they think the worms will consume and which ones they won't.Students will then test their hypothesis by first using the above directions to prepare the food testing tub. Once the tub is prepared students will place 4-5 worms into the tub and observe for about fifteen minutes or more (depending on the time allotted by the teacher). Students will then observe which foods were eaten and which weren't. They will then discuss if their hypothesis was accepted or rejected. They can then continue to discuss the reasons why their hypothesis was accepted or rejected and then brainstorm a list of new foods that might be consumed by the worms. If there is time or the teacher would like to experiment further you can use the new lists of food compiled by the students and repeat the experiment again. The worms can also be left in the tub for a longer period of time in order to ensure that the worms have an ample amount of time to consume the different foods. Lesson plan Before the experiment begins the teacher will have had to prepare the earthworm ecosystem. To prepare the ecosystem use the following instructions: # Take a clear 2 liter soda bottle. # Rinse the bottle thoroughly with warm water only and remove the outside label. # Mark a line all along the plastic indent where the top of the label usually begins. # Cut along the line you have just marked. # Using an electric drill (or other sharp tool) to poke four to five holes in the bottle cap. # Poke four to six holes in the bottom of the bottle for drainage purposes. # Poke ten to twelve holes in the top half of the bottle for air circulation. # Add clean, washed gravel into the bottle. # Next add a layer of moist bedding material. # Next, add a layer of dark potting soil. # Add a layer of moist sand. # Add a second layer of dark potting soil. # Next, add a thin layer of organic matter(should this be kept in the ecosystem or will it interfere with the food experiment?). # Finally add your worms to the ecosystem (no more than five per bottle) # Place the ecosystem on a foil pie plate or other plate so that the water from the soil does not drip everywhere. # Cover the entire bottle with tin foil so as to keep the ecosystem as dark and cool as possible. Be sure to make sure air is still able to flow into the bottle. # Store the ecosystem at room temperature or slightly below. From here, the students will be ready to begin the experiment. The problem that should be presented to the students is "What do our earthworms like to eat?" Students will then form and write down a hypothesis as to which of the four types of food the earthworms like to eat. Begin the experiment by setting up the food tub using the set-up handout listed above. Observe the earthworms in the food tub for about fifteen minutes, or more if you have time. Record your observations, even ones that don't necessarily don't have to do with the worms eating the food. After your time is up place the worms back into their ecosystem and answer the questions: "Which foods did our earthworms like?" and "Which foods did our earthworms dislike?" After answering those two questions return to the students' hypotheses and discuss whether they were accepted or refuted. Discuss together why they were accepted or refuted. Discuss other possibilities for food choices based on your results. If desired, repeat the experiment using new foods. Side Activity Before the experiment begins the teacher can take photos of the earthworm ecosystems created in the soda bottle (Figure 2). Earthworms tend to mix the layers within their enviroment. Having photos before, during, and after the experiment, combined with observation by the students will allow students to access the changes in the worm environment, creating a fun side project for the students. For our experiment we started by taking a picture within the first hour our ecosystem was created. Potential pitfalls No pitfalls have been currently determined because the experiment has not yet been performed. One possible pitfall may be that fifteen minutes is not ample time for the worms to eat or try all of the foods. This may hinder an accurate test of the students' hypotheses. One way to try and eliminate this issue is to alot as much time for the experiment as possible. Another helpful factor to eliminate this problem is by adding more than one worm into the tub at one time so that the chances that at least one of them will eat are higher than if there were only one or two worms. Math connections Once the children have recorded and discussed their finding in their groups, the students can decide which foods worked the best and which foods the earthworms did not like to eat. The children can work on making a bar graph perhaps to show their findings. They can also record how many of each type of food was placed in the tub in the beginning and how much was left at the end, once they have done this, the students can then compare the numbers deciding which type of food went faster and which type of food has more left over. Literature connections The Diary of a Worm by Doreen Cronin Connections to educational standards S3-4:2 Students demonstrate their understanding of predicting and hypothesizing by identifying simple patterns of evidence used to develop a prediction and propose an explanation. S3-4:4 Students demonstrate their ability to conduct experiments by referring to and following a detailed plan for an investigation and clearly describing evidence and quantifying observations with appropriate units and recording data at various points during an investigation by reporting what actually happens, even when data conflicts with expectations. Next steps Now that the experiment is complete you can take the experiment one step further and have the students research why the worms chose the foods they did. Have them research things such as how worms choose foods. Do they use sight, smell, or touch to determine what the food is, or do they even determine what it is at all? Have the students research the worm's digestive system as a means to discover if some foods can even be digested by worms at all. Students can also research how the different types of foods the worms eat affects their environment and more specifically their ecosystem. This experiment can branch out to many other little experiments or research projects that are beneficial to students learning about worms and their environment. Citations and links Worm Watch Canada 2002 Vermont State Grade Expectations can be found at the State of Vermont Department of Education website. http://education.vermont.gov/new/html/pgm_curriculum/science/gle.html